Depression in Intractable Partial Epilepsy Varies by Laterality of Focus and Surgery

Purpose: Depression sometimes occurs after surgical treatment for medically intractable partial epilepsy. The risk of pre‐ and postsurgical depression may vary by laterality of seizure focus. We reviewed the pre‐ and postsurgical psychological assessments and clinical courses of patients to identify those at highest risk for postsurgical mood disorders. Methods: Depression status was assessed in a consecutive series of epilepsy patients before and 1 year after epilepsy surgery with the use of Scale 2 of the MMPI‐2 and a clinical depression index (CDI) scoring the occurrence of depressive symptoms, psychiatric referral, or attempted/completed suicide. Outcome at 1 year was modeled by regression techniques as functions of preoperative mood measurements, side of epilepsy surgery, and preoperative verbal intelligence. Results: The CDI and Scale 2 MMPI‐2 correlated significantly (r = 0.341; p ≤ 0.01). Left (n = 54 subjects) and right (n = 53) surgery groups did not differ by sex, seizure outcome, age, education, age at first seizure, duration of epilepsy, or intellect. Higher presurgical depressive morbidity (p = 0.0037) and right‐sided surgery (p = 0.0003) predicted higher postoperative CDI. Higher preoperative Scale 2 scores, indicating worse depressive traits, predicted worse postoperative Scale 2 scores (p < 0.0001). Although side of surgery did not predict Scale 2 scores, Scale 2 scores of patients with preoperative right‐sided foci tended to have worse postsurgical Scale 2 scores (p = 0.08). Findings for the temporal lobectomy subgroup (n = 90) were similar to those of the overall sample. Conclusions: Patients undergoing right hemispheric epilepsy surgery, especially those with high presurgical depression–related morbidity, may be particularly susceptible to clinical depression. Our findings support other studies that show an interhemispheric modulation of depressive traits and symptoms.